[12:35] <xandey> Hi Kernel Team, I'm trying to bisect a bug which is in ubuntu releases, but doesn't show up in mainline builds. Is there some way to get the git history back to a mainline build? I can't seem to find this history in ubuntu-bionic.git
[12:38] <cascardo> xandey: you can use the 4.15 tag, and the Ubuntu-4.15.0-* tags
[12:46] <xandey> cassardo: ah, i was looking for v4.15.17. Also, I wasn't able to build commits which have labels like "UBUNTU: Ubuntu-4.15.0-4.5" but aren't actually tagged... is it possible this is some sort of rebase or toolchain change?
[12:47] <xandey> cassardo: some of them ask me to change config options when following https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel
[13:15] <cascardo> xandey: yes, very likely a rebase
[13:15] <cascardo> during development, those kernels are based on rc releases
[13:16] <cascardo> further down the stable pipeline, you will more likely see kernels all based on v4.15
[13:16] <cascardo> and fast-forward, all of those reachable from the master branch, at least after the GA kernel
[13:17] <cascardo> but as we are so close to GA, the oldest one you will find is Ubuntu-4.15.0-9.10
[13:27] <xandey> caascardo: right, I confirmed that I get the issue with 4.15.0-9.10 (building myself and downloading prebuilt from launchpad). However, I don't see the issue in any of the mainline built kernels 4.15.0-rc1, 4.15.17, 4.17.0-rc6.
[13:30] <xandey> cascardo: I guess i'm looking to see if there's any more narrowing I can do at this point. But perhaps this is as good as I can do here, and it's time to try and debug directly.
[13:34] <cascardo> what's the issue? did you report a bug already?
[13:34] <xandey> yeah: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1768139
[13:35] <xandey> it's a kernel crash when a dell laptop is connected to hdmi and boots up, but only with ubuntu kernel
[13:35] <xandey> i was trying to do the rebase for the bug report
[13:35] <xandey> sorry, *bisect*
[13:36] <xandey> although I didn't see that last comment yet
[13:52] <cascardo> xandey: you don't happen to have a Thinkpad X1, do you?
[13:57] <xandey> nope, dell insprion 15
[13:58] <xandey> cascardo: Dell Inspiron 7559
[14:17] <cascardo> ok, i915 change in 4.15.0-9 was related to X1 only
[14:40] <xandey> well, it's not that I narrowed it down to 4.15.0-9, it's only that that's as far back as I was able to build.
[14:42] <xandey> Oh, looking back at my notes, it looks like I also managed to test 4.15.0-1_4.15.0-1.2 which asked me to change some cofig options, but also displayed the issue.
[14:45] <xandey> I could try reverting dc0f16f9b5084e6be2b8c79f8c6cd499a3451791 which appears to be the only change between 4.15 and  4.15.0-1_4.15.0-1.2 in drivers/gpu/drm/i915
[14:47] <xandey> but I don't see that as a difference between the 4.15.17 from linux-stable and 4.15.0-24 
[14:50] <xandey> anyway, I don't mean to take up your time with a low priority bug, I just thought perhaps I was missing something with the build setup.
[15:09] <cascardo> looking at the stack trace and the diff, it's hard to think this would be specific to ubuntu kernels
[15:10] <cascardo> did you try our mainline builds?
[15:11] <xandey> yes, I tried the ones from http://kernel.ubuntu.com/~kernel-ppa/mainline/?C=N;O=D I also built the mainline myself
[15:11] <xandey> maybe some sort of module packaging difference?
[15:14] <cascardo> well, enabling some drm debug could help
[15:15] <xandey> could you direct me a bit there?
[15:16] <xandey> drm.debug=0xe on kernel command line?
[15:17] <cascardo> something like that, let me look at the interesting bits of i915 and see which flag would trigger them
[15:23] <cascardo> =0x4
[15:23] <cascardo> KMS seems to have most of it
[15:35] <xandey> okay, i'll try that
[16:42] <xandey> cascardo: I grabbed two traces of the log, I think it will take me a while to puzzle out them. I posted them to the bug.
[17:30] <cascardo> xandey: thanks
[17:38] <xandey> cascardo: no problem